Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/38—Electroplating: Baths therefor from solutions of copper

Definitions

• ABSTRACT An acid copper plating bath which contains a copper metal salt and a minor amount of a sulfoniumalkanesulfonate or sulfoniumalkanecarboxylate as a brightening agent.
• lllustrative sulfonium compounds are N-cyclohexyl-2-benzothiazol sulfonium-l propanesulfonate, bis (dimethylthiocarbamyl) sulfonium-l-propanesulfonate, and his (dimethylthiocarbamyl) sulfonium-l-propanecarboxylate.
• Preferred amounts of the sulfonium compounds range from about 0.001 to 1.0 grams per liter. The use of such acid copper plating baths in the electrodeposition of copper metal is also disclosed.
• the present invention relates to the electroplating of copper from an aqueous acidic bath. More particularly the invention pertains to an acid copper platingbath containing a minor proportion of a novel brightening agent.
• Brightening agents such as the organic sulfonic acids and carboxylic acids or their salts offered considerable promise but suffer from certain serious disadvantages. For example, these brighteners have a limited low current density brightness range.
• novel sulfonium sulfonate or earboxylate brightening agents of this invention have the following formula:
• each R radical which may be the same or different, is selected from the group, consisting of hydrogen; alkyl having from one to eight carbon atoms, for example; methyl or ethyl; aryl having from six to 12 carbon atoms, for example; phenyl or naphthyl;
• each R radical may be the same or different and is a lower alkyl having from one to six carbon atoms; and r is l or zero; n is an integer from 1 to 6; R" is selected from the group consisting of hydrogen and the methyl radical; and Z is an anion selected from the group consisting of S0 and COO.
• the preferred brightening agents are those of the general formula wherein r is zero and each R is lower alkyl having from one to six carbon atoms; Z is SO; and n is an integer from 1 to 6. Especially preferred is the brightening agent wherein eachR' is methyl; n is 3; Z is S0 and r is zero.
• r is zero and each R is lower alkyl having from one to six carbon atoms; Z is SO; and n is an integer from 1 to 6.
• eachR' is methyl; n is 3; Z is S0 and r is zero.
• other brightening agents of this invention also provide satisfactory results.
• dialkylsulfoniumalkanesulfonates having from one to 18 carbon atoms in the alkyl radical
• Typical sulfoniumalkanesulfonates include for example: N-cyclophenxyl-2-benzothiazol "sulfonium-1- propanesulfonate;
• R is a lower aliphatic radical
• Q and Q are selected from the group consisting of hydrogen, lower alkyl and lower hydroxy-alkyl
• X, Y and Z are selected from the group consisting of oxygen, sulfur, nitrogen, and the imino radical, at least one of them being sulfur
• X, Y', and Z are selected from the group consisting of oxygen, sulfur, nitrogen and the imino radical, at least one of them being sulfur.
• sulfoniumalkanecarboxylates which can be effectively employed as brightening agents in the practice of the present invention are similar to the above described classes of sulfoniumalkanesulfonates except that a carboxyl radical is substituted for the sulfonate radical.
• Typical sulfoniumalkanecarboxylates include:
• Bis(dimethylthiocarbamyl)sulfonium-Lpropanesulfonate can be prepared by the reaction of tetramethyl thiuram monosulfide and propane sultone in accordance with the procedure described by Gaertner in U.S. Pat. No. 2,813,898.
• Other sulfonium sulfonates can be prepared by the same general procedure utilizing the appropriate sulfides and sultones.
• the corresponding bis(dimethylthiocarbamyl)sulfonium-l-propanecarboxylate can be prepared by the Gaertner procedure, except that propriolactone is substituted for the propane sultone.
• novel stable brightening agents of this invention may be employed by themselves to obtain very satisfactory brightening effects in the electroplating of copper, they may also be utilized in conjunction with known brightening agents or other additives to improve further the brightening and leveling.
• the use of the brightening agents of this invention in conjunction with such prior art substances as the carbon-oxygen compounds disclosed in U.S. Pat. No. 3,288,690; polyethylene glycols and methoxy polyethyleneglycols imparts excellent brightness and leveling qualities to the electroplated product.
• the qualities of the electroplated end product can be enhanced by the inclusion in the electroplating bath of such materials as amine dyes such as described in U.S. Pat. Nos.
• Preferred other additives include polyethylene glycols and methoxy polyethylene glycols such as Carbowax 5000 having a molecular weight range of 2,000 to 6,000; aminothiazoles and aminothiazolines such as 2- thiazolidinethione; and dyes such as Methyl Violet, Crystal Violet, and Fuchsin. Mixtures of these other additives may also be employed. In general, these other additives are utilized in minor, conventional amounts.
• a minor but effective amount of the novel brightening agents of this invention are incorporated into the aqueous plating bath prior to the inception of the electrolytic plating operation.
• the amount of the novel brightening agent to be incorporated into the'plating bath should be sufficient to obtain the brightening effeet desired in each particular case as may be determined by the worker skilled in the art. It has been found in practice that satisfactory results are obtained when the novel brightening agents are present in the electrolyte plating bath in a concentration of from about 0.0001 to 1.5 grams per liter, and most preferably from 0.001 to L0 gram per liter.
• the usual bath will have the following composition:
• the sulfuric acid may be substituted with sulfamic or fluoboric acids, while the copper may be salts of other acids such as sulfamic or fluoboric.
• Example 3 The procedure of Example 1 was followed except that the following materials were also incorporated into the plating bath Material Concentration Carbowax 5000 0.4 gm./liter Methyl violet 0.0l5 gm./liter The copper deposit on the plated material was very bright and leveled in the range of from 1 to l00 ASP,
• Example 3 Material Concentration Carbowax 5000 Methyl violet 2'Thiazolidienethione 0.4 gmJliter 0.015 gm./liter 0.001 gmJliter EXAMPLE
• the electroplating bath of Example 3 was set aside and allowed to remain standing for a period of 30 days. Thereafter, Hull cells were rerun in accordance with the procedure set forth in Example 1 yielding a plated final product which showed no substantial deterioration of the brightness or low current density dullness. In addition no brightener decomposition products formed in the plating tank.
• an acid copper electroplating bath containing a salt of copper and a free acid as the essential constituents, the improvement which comprises the addition to said bath of an amount, sufficient to provide a bright electrodeposit, of a sulfoniurn compound having the structure wherein R is a radical selected from the group consisting of hydrogen; alkyl having from one to eight carbon atoms; aryl having from six to 12 carbon atoms;
• R is a lower alkyl radical having from oneto six carbon atoms, and r is l or zero; n is an integer from 1 to 6; .R" is selected from 'thegroup consisting of hydrogen and methyl; and Z is an anion selected from the group consisting of S0 and COO. 2. 1n the acid copper plating bath of claim 1 wherein the sulfonium compound is added to said bath in an amount ranging from about 0.001 to 1.0 gram per liter.
• the sulfonium compound is N-cyclohexyl-2- benzothiazol sulfonium-l-propanesulfonate.
• the sulfonium compound is bis(dimethylthiocarbamyl) sulfoniuml -propanesulfonate.
• the sulfonium compound is bis(dimethylthiocarbamyl) sulfoniuml -propanecarboxylate.
• the sulfonium compound is bis(benzothiazole)sulfonium-l -propanesulfonate.
• the bath also contains a glycol selected from the group consisting of polyethylene glycol and methoxypolyethylene glycol in an amount sufficient to enhance the brightness of the electrodeposit.
• the step which comprises electrolyzing an aqueous acid copper solution containing a copper metal salt and an amount, sufficient to provide a bright electrodeposit, of a sulfonium compound having the structure.
• R is a radical selected from the group consisting of hydrogen; alkyl having from one to eight carbon atoms; aryl having from six to 12 carbon atoms;

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Manufacturing Of Printed Wiring (AREA)

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Cited By (24)

Citations (10)

• 1972
  • 1972-04-27 US US00248160A patent/US3725220A/en not_active Expired - Lifetime
  • 1972-11-02 GB GB5059472A patent/GB1354840A/en not_active Expired
  • 1972-11-13 DE DE2255584A patent/DE2255584C2/de not_active Expired
  • 1972-11-14 FR FR7240334A patent/FR2186544B1/fr not_active Expired

Patent Citations (10)

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